The present invention relates to centralization tools, and more particularly, to the use of expansion tools comprising an expander and an actuator configured to centralize a casing-casing annulus in a wellbore.
The development of directional drilling technologies allows for strongly deviated boreholes. The use of horizontal or otherwise deviated drilling provides several advantages including making it possible to reach reservoirs miles away from the wellhead. This is especially useful if the reservoir is located in an area where vertical drilling is not possible or is undesirable such as under a lake or an environmentally sensitive area. In practice, true vertical wellbores are difficult, if not impossible, to achieve. In other words, vertical wellbores typically have at least some intervals or sections that are deviated.
In some cases, directional drilling may be used to drill a new wellbore originating from an existing wellbore. For example, one may insert a kick-off device, such as a whipstock assembly, vertically down to a kick-off point and then initiate directional drilling within the existing wellbore. Directional drilling is often desirable because it increases the exposed section length through the reservoir and allows more wellheads to be grouped together at one location at less cost, which should result in fewer rig moves, and less surface area disturbance.
Over the past several decades, drilling operations have left many wells depleted or economically unviable. Some of these wells have been left uncemented but still contain nested casing strings having an inner casing or tubular arranged within an outer casing or tubular. For example, FIG. 1A shows a cross-sectional top view of an inner casing 14 longitudinally arranged within an outer casing 16, and FIG. 1B depicts a cross-sectional side view of the inner casing 14 as arranged within the outer casing 16. An annulus 15, oftentimes being referred to as the casing-casing annulus (CCA), is generally defined between the inner and outer casings 14, 16. When the inner casing 14 is not properly centralized or cemented within the outer casing 16, the inner casing 14 is effectively free to move radially within the outer casing 16. Because true vertical wells rarely exist in practice, over time, the inner casing 14 may tend to lean towards the outer casing 16 at certain points due to factors such as gravity, thereby resulting in a non-concentric annulus 15.
As depicted in both FIGS. 1A and 1B, the inner casing 14 has come into contact with the outer casing 16. As a result, at least a portion of the annulus 15 exhibits zero clearance or stand-off distance between the outer radial surface of the inner casing 14 and the inner radial surface of the outer casing 16. As used herein, “clearance” or “stand-off distance” refers to the minimal distance between casings in a casing-casing annulus. For the purposes of this disclosure, the terms “clearance” and “stand-off distance” may be used interchangeably. Non-concentric annuli may lead to gas channeling problems during subsequent intervention operations (e.g., kickoff, lateral, etc.). Moreover, an annulus 15 exhibiting poor clearance or stand-off will also suffer from poor displacement efficiency of fluids.
One way to maximize the clearance of a casing-casing annulus is to use centralizers configured to center the inner casing 14 relative to the outer casing 16. Typical centralizers include bow springs and solid centralizers. The use of bow springs, however, is often limited to vertical and low angle wells since they have high associated running forces and may collapse under casing weight in higher angles. Solid centralizers were introduced largely because of the shortcomings of bow springs. Unfortunately, however, the use of solid centralizers is often time consuming, expensive, and waste apparent.